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Check types in assigment

Not all the types are compatible in assigment, so a check is needed
before the assigment.

--- a/expr.c

+++ b/expr.c

@@ -37,7 +37,37 @@

 	return bincode(op, np1->type, np1, np2);

 }

+/*

+ * Convert the second Node to the type of the first

+ */

 static Node *

+convert(Node *np1, Node *np2)

+{

+	Type *tp1, *tp2;

+	register uint8_t t1, t2;

+

+	tp1 = UNQUAL(np1->type), tp2 = UNQUAL(np2->type);

+	if (tp1 == tp2)

+		return np2;

+	t1 = tp1->op, t2 = tp2->op;

+

+	switch (t1) {

+	case ENUM: case INT: case FLOAT:

+		switch (t2) {

+		case INT: case FLOAT: case ENUM:

+			return castcode(np2, tp1);

+		}

+		break;

+	case PTR:

+		switch (t2) {

+		case ARY: case FTN:

+			/* TODO: take address of np2 */;

+		}

+	}

+	return NULL;

+}

+

+static Node *

 arithmetic(char op, Node *np1, Node *np2)

 {

 	char *err;

@@ -423,7 +453,8 @@

 static Node *

 assign(void)

 {

-	register Node *np = bit_or();

+	register Node *np1 = bit_or(), *np2;

+	char *err;

 	for (;;) {

 		register char op;

@@ -443,11 +474,23 @@

 		default:  goto return_np;

 		}

 		next();

-		/* TODO: cast types */

-		np = bincode(op, np->type, np, assign());

+		np2 = assign();

+		if (!np1->b.lvalue)

+			goto nolvalue;

+		if ((np2 = convert(np1, np2)) == NULL)

+			goto incompatibles;

+		np1 = bincode(op, np1->type, np1, np2);

 	}

 return_np:

-	return np;

+	return np1;

+

+nolvalue:

+	err = "lvalue required as left operand of assignment";

+	goto error;

+incompatibles:

+	err = "incompatible types when assigning";

+error:

+	error(err);

 }

 Node *